textproduct: Quad Cities

KEY MESSAGES

- Rounds of nocturnal and diurnal convection through tonight will bring a risk of locally heavy rainfall due to weak winds aloft. If storms stall or repeat over the same areas, flash flooding is possible.

- Heat and humidity will return around mid-week with temperatures in the 90s and heat indices pushing 100 or higher. The probability of heat headlines around mid-week is 33-40 percent.

SHORT TERM /THROUGH TONIGHT/

Issued at 137 AM CDT Mon Jun 8 2026

The heavy rain yesterday focused around a weak boundary located near I-80. Said boundary is still present and runs from near KC75 to near KGGI. A secondary but much more subtle boundary runs from near KAAA to near KIKV.

Through sunrise and through Monday, PWATs are progged to be 1.5 to near 2 inches and winds aloft are still weak. Warm rain processes should dominate creating very efficient rainfall rates. Storm scale processes will produce additional boundaries thus raising the probability that storms may repeat over the same areas and cause flash flooding.

The 00z REFS LPMM is suggesting the potential for 2.5 to 3+ inches of rain near the boundary in southeast Iowa and more localized areas north of I-80. More disturbing and much higher numbers from the REFS LPMM are showing up this afternoon in northwest Illinois.

Based on this the flash flood watch is being expanded to the entire area. If storms stall or repeat over the same areas, rainfall rates of 2 to 3 inches an hour for two or more hours are very possible.

By evening, the upper level low will exit the area and rain will quickly end from west to east. However, with a weak high building into the area, winds will turn light overnight. The light winds and wet ground raises the prospects of fog development. Right now HREF probabilities for visibilities under 1 mile are 20-30%. The fog potential will need to be re-evaluated to see if probabilities increase over the next 12-18 hours.

LONG TERM /TUESDAY THROUGH SUNDAY/

Issued at 137 AM CDT Mon Jun 8 2026

Tuesday through Monday Assessment...high (>80%) confidence of temperatures well above normal. Low (20-25%) confidence for rain.

If fog develops Monday night, that will play significantly into how warm it will get on Tuesday. The model trend of above normal temperatures through Friday remains solid.

As mentioned yesterday, the highest heat indices are Tuesday/Wednesday. A strong front is forecast to move through the area Wednesday night or Thursday that will bring cooler temperatures for next weekend.

Heat indices Tuesday continue to indicate 95 to 100 but areas south of I-80 have a 30-40% probability of exceeding 100. On Wednesday the probability of seeing heat indices of 100+ is now at 50-60%. Depending upon how rain chances play out, heat headlines may be needed in the Tuesday/Wednesday time frame.

The model consensus currently has 20-40 percent rain chances mainly north of I-80 Tuesday night. These chances may push further north if the heat dome builds quicker into the area. The storms running around the edge of the heat dome would have the potential to be severe. The primary severe risk would be damaging winds. SPC does have a marginal risk for the area, but mainly for Tuesday night.

Wednesday night into Thursday looks interesting.

A stronger front is progged to move through the area that will be associated with a strong upper level disturbance. Winds in the mid- levels of the atmosphere are progged to be around 50 knots indicating organized storms with the potential for severe storms. CSU ML progs and other ML analog sites have a 30-45% probability of damaging winds occurring Wednesday/Wednesday night. However, large hail and tornadoes cannot be fully ruled out. Depending upon the timing of the front, strong to severe storms may persist into Thursday.

Wednesday night has the best chances for rain. The current model consensus has 60-90 percent chances for rain. Outside of Wednesday night, the model consensus has daily 20-40 percent chances for rain Friday through Monday.

AVIATION /12Z TAFS THROUGH 12Z TUESDAY/

Issued at 634 AM CDT Mon Jun 8 2026

Widespread showers and isolated thunderstorms continue to lift northward across the area early this morning. Mainly IFR to LIFR conditions are being reported with brief improvement to MVFR to VFR in no precipitation. Used tempo groups in the first 4 hours in areas of higher confidence where showers and storms will occur and use prob30 after that. IFR conditions are expected through the day with some improvement after 21 UTC. Widespread showers and storms are expected through late morning before showers and storms become more isolated during the afternoon. Winds are forecast to become light and variable after 00 and this may lad to fog development across the area with at least MVFR visibilities possible.

DVN WATCHES/WARNINGS/ADVISORIES

IA...Flood Watch through this evening for IAZ040>042-051>054- 063>068-076>078-087>089-098-099. IL...Flood Watch through this evening for ILZ001-002-007-009- 015>018-024>026-034-035. MO...Flood Watch through this evening for MOZ009-010.